Angiosperm anatomy and physiology

Question ?

• What heading can be given to the following groups of words?

Question ?

• What is a vegetable?

• What is a fruit?

THM (take home message)

• Plants have organs too, just like animals.

• Asexual organs (vegetables)

• Sexual organs (fruits)

Plant Cell Types

• Differentiated by the type and thickness of the cell wall.

1. Parenchyma (soft tissue)

2. Collenchyma (glue tissue)

3. Sclerenchyma (hard tissue)

Parenchyma Cells

• Primary wall only.• Thin cell wall.• Alive when mature, • “typical" plant cell.

Functions

• Ps

• Storage

• "Filler" cells

• Cell division (mitosis)

Collenchyma

• Primary wall only.

• Wall is thickened, especially in the corners.

• Alive when mature.

Function

• Support of non-woody plant parts.

• Ex: veins, stems.

Sclerenchyma

• Secondary wall present.• Wall strengthened with

lignin.• Dead when mature.

Sclerenchyma Types

1. Fibers

2. Sclereids

3. Tracheids

4. Vessel Elements

Fibers

• Elongated thin cells used for support.

• Ex: Hemp fibers

Sclereids

• Used for hard dense areas and support.

• Ex: Nut shells, seed coats

Tracheids

• Spindle - shaped cells with pits in the cell walls.

• Used for water transportation.

Vessel

Fiber

Vessel Elements

• Wide stocky cells with pits in the side walls; lack end walls.

• Used for water transportation.

Plant Tissues

• Can be named by several methods:– Ex: Cell Location

Cell Origin Cell Function

Main Tissue Systems

1. Dermal

2. Vascular

3. Ground

Dermal Tissue

• Epidermis or "skin" of the plant.• Often has a cuticle, a waxy coating to prevent

water loss.• Functions:

– Prevent water loss.– Water absorption (root hairs).

Vascular Tissue

• Made of Xylem and Phloem.

• Functions:– Transport and support– Xylem - Water– Phloem - Food

Xylem

Phloem

Phloem

• Sieve Cell – alive when functioning, but lacks a nucleus.

• Companion Cell – alive, controls itself and the sieve cell.

Ground Tissue

• Tissue between the dermal and the vascular tissues.

• Functions:– "Filler" tissue– Ps– storage– support

Asexual Organs

1. Stem

2. Leaf

3. Root

Stem

• The main body of the portion above ground of a tree, shrub or herb.

• The ascending plant axis.

Stem Functions

• Support of other plant organs.

• Ps.

• Storage (water and food).

Leaf

• Lateral outgrowths of the stem axis.• Primary photosynthetic organs.• Function:

– Photosynthesis

– Storage

Root

• The descending axis of a plant, normally below ground.

• Functions:– Anchorage.

– Absorption of water and minerals.

– Storage.

Sexual Organs

1. Flowers

2. Fruits

3. Seeds

Flowers

• Modified leaves grouped together on a stem.

• Sexual reproductive organs.

• Function:– Sexual Reproduction

Fruit

• A mature ovary, sometimes including other floral parts.

• Function:– Seed dispersal– Seed protection

Seed

• Mature ovule containing the embryo and nutrient tissues.• Function:

– Dispersal unit in sexual reproduction.

– Johnny Appleseed–

“A far greater natural source of cyanide is the cassava root, a vegetable favored by many in Africa. (Westerners know this plant best as tapioca.) Drying, soaking, and baking cassava roots renders its cyanide precursor, linamarin, harmless, but if that process is not carried out properly the cassava can remain poisonous. “

A nice Question

• How does plant growth and animal growth differ ?

Animals

• Whole organism increases in size to a certain size...

Determinant Growth: grow to a certain size, then stop.

Plants

• Growth in specialized areas only.

• Indeterminant Growth: grow as long as they live because the specialized areas remain embryonic.

Plant Meristems• Perpetual embryonic

regions.• Zones for cell division.

Meristem Types

1. Apical growth in length. Primary growth.

2. Lateral/Cambiums growth in diameter. Secondary growth.

Comment

• Some tissues like Xylem may be Primary or Secondary depending on which meristem produced the cell.

• Ex:– Primary xylem from apical meristem– Secondary xylem from lateral meristem

• This is important when we speak of “wood”

Apical Meristem Types

1. RAM – Root Apical Meristem: primary growth of roots.

2. SAM – Shoot Apical Meristem: primary growth of shoots.

RAM

• Located at the tip of each growing root.

• Protected from the soil by the Root Cap.

RAM

Root Cap

• Protects RAM.

• Secrets a polysaccharide lubricant for root growth.

Root Zones

1. Cell Division - cells small and embryonic.

Cell Differentiation Begins in Primary Tissues (also known as primary

meristems)

2. Cell Elongation - cells elongate and start to mature.

3. Cell Differentiation - cells mature into final cell types.

Root Hairs

• Extensions of the epidermis to increase surface area for water absorption.

• Not a true tissue.• Comment - root hairs are very delicate and

must be continually replaced.

Root Hairs

RAM - Primary Tissues

1. Protoderm – matures into epidermis

2. Procambium – matures into vascular tissue

3. Ground Meristem – matures into ground tissue

Root Types

• Taproot - one main root.– Ex: carrot

• Fibrous Roots - many small roots of equal size.– Ex: grass roots

• Adventitious Roots– Roots that develop from other plant parts.– Ex: roots on stem cuttings, climbing roots

SAM Produces

1. Protoderm2. Procambium3. Ground MeristemComment – these tissues mature into the same

things as seen in RAM.

SAM Differences

• No "root" cap.

• Produces leaves as stem out-growths at the nodes.

• Has buds.

Buds

• Apical Meristems protected by modified leaves or bud scales (can see these NOW!!!).

• Axillary Buds

Branch Stems

• Develop from axillary meristems or axillary buds.

• "External" development.

Modified Stems

1. Rhizomes

2. Stolons

3. Tubers

4. Tendrils

Rhizome

• An elongated

underground horizontal stem.

• Ex: Iris, many grasses

Stolon

• An elongated

above-ground horizontal stem.

• Ex: Strawberries Airplane Plant

Tuber

• A much-enlarged, short,

fleshy underground stem tip.

• Ex: Dahlia, Potato

Tendril

• A slender coiling stem.

• Ex: Clematis and other climbing vines.

• Also occur on leaves of some plants

Leaves

• Stem outgrowths for Ps.

• Leaf Morphology:1. Gross

2. Fine

Gross Morphology

• Blade - the flattened portion of a leaf.

• Petiole - stalk of a leaf.

Blade

Petiole

Axillary Buds

Blade/Leaf Types

• Simple - 1 blade.

• Compound - Several blades.

Nodes and Internodes

• Node - stem area where a leaf and bud are attached.

• Internode - stem area between nodes.

Nodes

Internode}

Fine Morphology

• The tissues within a leaf.

1. Upper Epidermis

2. Mesophyll

3. Lower Epidermis

4. Veins

Upper Epidermis

• Cuticle present.

• Usually 1 cell layer thick.

• Cells w/o chloroplasts .

• Function: protects the mesophyll.

Mesophyll

1. Palisade upright cells.2. Spongy loosely organized

cells with air spaces.

• Function: major sites for Ps.

Epidermis

Epidermis

Lower Epidermis

• Cuticle present.

• Usually 1 cell layer.

• Cells w/o chloroplasts.

• Stomata present for gas exchange.

Stomata (Plant Breathing)

• Regulated by Guard Cells

Vein Structure

• Xylem: dorsal

• Phloem: ventral

• Often surrounded by bundle sheath cells for support.– What type of cells are these?– When have we talked about them before??

Xylem

Phloem

Bundle Sheath Cells

Collenchyma

Leaf Modifications

1. Tendrils: for support Ex: Peas

2. Bulbs: for food storage Ex: Onion

3. Insect Catching Ex: Carnivorous Plants

4. Flowers: thought to be modified leaves.

Tendrils Spines

Succulent Leaves Bracts

Other Modifications of Leaves

Stem Vascular Tissue

• Dicots – vascular bundles join together to make a ring. Often have secondary growth.

• Monocots – vascular bundles are scattered. No true secondary growth.

Secondary Growth

• Growth in diameter.

• Growth from lateral meristems or cambiums.

Cambium Types

1. Vascular – produces xylem and phloem.

2. Cork – produces “cork”…..(bark).

Vascular Cambium

• Location: between primary xylem and phloem.

• Produces: secondary xylem and phloem.

Fibers

Phloem

Vascular Cambium

Xylem

Fibers

Vascular Cambium: Cell Maturation

• Internal xylem

• External phloem

• The VC pushes the xylem and phloem apart from each other.

Result

• Newest xylem is next to the cambium.

• Oldest xylem is in the center of stem.

Result

• Newest phloem is next to cambium.

• Oldest phloem is under the epidermis.

Result

• Xylem accumulates over time.

• Phloem is destroyed by the outward growth and must be replaced yearly.

Cork Cambium

• Location: Cortex (external to the VC).

• Produces: Cork

• Comment – commercial cork is harvested from a Cork Oak.

Cork Cells

• Produced "outwardly" only.

• Covered with suberin and are dead when mature.

• Function – insulation and protection.

Vascular Cambium

Cork Cambium

Phloem

Xylem

Fibers

Cortex

Epidermis

Bark

• All tissues external to the VC.• Includes:

– Phloem (1 degree and 2 degree)– Cork – Cortex– Epidermis– Fiber cells

Wood

• Xylem tissue of a dicot stem.

• Comment – monocots don’t have VC and technically don’t produce true “wood”.

Xylem Growth

• Springwood - Large cells Rapid growth

• Summerwood - Small cells Slow growth

Annual Rings

• Formed by the growth difference between springwood and summerwood.

• Usually one produced per year.

Comment

• Ring size varies by climate and growing conditions.

• Rings can be used to date wooden structures.

Summer Wood

Spring Wood

One Year’s Growth

Monocots vs. Dicots

1. Seeds and embryos

2. Leaves

3. Stems

4. Roots

5. Flowers

Seeds and Embryos

• Dicots - no endosperm. - 2 cotyledons.

• Monocots - endosperm - 1 cotyledon

Leaves

• Dicots – netted veins.

• Monocots - parallel veins.

Stems

• Dicots - ring pattern - vascular cambium

• Monocots - scattered pattern - no vascular cambium

Roots

• Dicots – taproot. – xylem centermost tissue.

• Monocots - fibrous roots. - pith centermost

tissue.

Flowers

• Dicots – parts in 4's or 5's.

• Monocots – parts in 3's.